A novel slurry for Cu films CMP in Ru-based Cu interconnects: Integration of experimental and theoretical calculations

Abstract

As technology nodes shrink below 10 nm, stricter demands are required for the one-step polishing of copper (Cu) films in ruthenium (Ru)-based Cu interconnects: a high Cu removal rate (RR) and a near-zero Ru RR. In this work, an eco-friendly slurry was newly formulated by combining hydroxyethylethylene diphosphonic acid (HEDP) and phytic acid (PA), both containing phosphate groups, to enhance corrosion inhibition and polishing performance during Cu/Ru CMP. Polishing and electrochemical experiments demonstrated that the synergistic inhibitors achieved a corrosion inhibition efficiency of 96 % for Cu. Under optimized conditions, the material removal rates (MRRs) of Cu and Ru reached 5432 Å/min and 10 Å/min, respectively, with a maximum removal rate selectivity (RRS) of 543:1 and surface roughness (Sqs) of 0.76 nm and 0.53 nm. Contact angle, coefficient of friction (COF), Ultraviolet–visible spectroscopy (UV–Vis), X-ray photoelectron spectroscopy (XPS) analyses confirmed the formation of a protective passivation film on Cu/Ru surfaces from both mechanical and chemical perspectives. Theoretical calculations identified the reactive sites of the inhibitors and simulated their adsorption behavior in a CMP environment, revealing that the synergistic inhibitors exhibited the highest adsorption energy. Without the use of surfactants, the multifunctional synergistic inhibitors improved surface quality through lubrication and passivation effects while reducing reagent consumption. This work provides both theoretical and practical guidance for the design of green and efficient CMP slurries in advanced semiconductor manufacturing.